Cart is empty
The Big Five Most Common Plant Pests
(And Their Solutions)
Spider MitesAlthough related to insects, mites are not insects but members of the arachnid class along with spiders and ticks.
IdentificationTo the naked eye, spider mites look like tiny moving dots; however, you can see them easily with a 10X hand lens. Adult females, the largest forms, are less than 1/20 inch long. Spider mites live in colonies, mostly on the under-surfaces of leaves; a single colony may contain hundreds of individuals. The names "spider mite" and "web-spinning mite" come from the silk webbing most species produce on infested leaves. The presence of webbing is an easy way to distinguish them from all other types of mites.
Life CycleIf temperature and food supplies are favorable, a generation can be completed in less than a week. Spider mites are generally favored by hot, dusty conditions. Plants under water stress are also highly susceptible. DamageMites cause damage by sucking cell contents from leaves. A small number of mites is not usually reason for concern, but very high populations—levels high enough to show visible damage to leaves—can be damaging to plants, especially herbaceous ones. At first, the damage shows up as a stippling of light dots on the leaves; sometimes the leaves take on a bronze color. As feeding continues, the leaves turn yellow and drop off. Often leaves, twigs, and fruit are covered with large amounts of webbing. Damage is usually worse when compounded by water stress. |
Treatment and SolutionsBiological ControlThere are numerous insects (lacewings and lady beetles) that prey on spider mites. However, the most commonly sold predators are other types of mites. Predatory mites (usually Phytoseiulus spp., Amblyseius spp. or Metaseiulus spp.) can be purchased and released onto infested plants. If predators are used, do not apply pesticides that will kill them. Cultural ControlCultural practices can have a significant impact on spider mites. Dusty conditions often lead to mite outbreaks. Keeping your growing areas clean is always a good idea. Water-stressed plants are less tolerant of spider mite damage. Regular, forceful spraying of plants with water will often reduce spider mite numbers adequately. Be sure to get good coverage, especially on the undersides of leaves. If more control is required, use an insecticidal soap or oil in your spray, but test the product on one or two plants to be sure it is not damaging to plants. Chemical ControlSpider mites frequently become a problem after the application of insecticides.
Recommended Products |
ThripsThrips are tiny, slender insects with fringed wings. They feed by puncturing their host and sucking out the cell contents. Pest species are plant feeders that scar leaf, flower, or fruit surfaces or distort plant parts.
IdentificationMost adult thrips are slender, minute (less than 1/20 inch long), and have long fringes on the margins of both pairs of their long, narrow wings. Immatures (called larvae or nymphs) are similarly shaped with a long, narrow abdomen but lack wings. Most thrips range in color from translucent white or yellowish to dark brown or blackish. A few species are more brightly colored, such as the distinctive reddish orange abdomen of larvae of the predatory thrips. Life CycleThe thrips life cycle includes the egg, two actively feeding larval (nymphal) stages, nonfeeding prepupal (propupal) and pupal stages, and the adult.
DamageThrips prefer to feed in rapidly growing tissue. Feeding by thrips typically causes tiny scars on leaves and fruit, called stippling, and can stunt growth. Damaged leaves may become papery and distorted. Infested terminals may discolor, become rolled, and drop leaves prematurely. Feces may remain on leaves or fruit long after thrips have left.
|
Treatment and SolutionsBiological ControlThrip predatory mites Pirate Bugs Predatory nematodes Green Lacewings Ladybugs Chemical ControlWhen chemical control is necessary, spray pesticides 2 to 3 times over a period of five days. Please note, this recommendation assumes greenhouse temperatures range from 70–85F. Recommended Products |
Aphids
Aphids are small, soft-bodied insects with long, slender mouth parts that they use to pierce stems, leaves, and other tender plant parts and suck out plant fluids. Many aphid species are difficult to distinguish; however, identification to species is not necessary to control them in most situations
IdentificationAphids may be green, yellow, brown, red, or black depending on the species and the plants they feed on. A few species appear waxy or woolly due to the secretion of a waxy white or gray substance over their body surface. All are small, pear-shaped insects with long legs and antennae. Most species have a pair of tube-like structures called cornicles projecting backwards out of the hind end of their bodies. The presence of cornicles distinguishes aphids from all other insects.
Life CycleAphids have many generations a year. Young aphids are called nymphs. They molt, shedding their skins about four times before becoming adults. There is no pupal stage. Some species mate and produce eggs in fall or winter, which provides them a more hardy stage to survive harsh weather. In some cases, these eggs are laid on an alternative host, usually a perennial plant, for winter survival.
DamageLow to moderate numbers of leaf-feeding aphids are usually not damaging. However, large populations cause curling, yellowing, and distortion of leaves and stunting of shoots; they can also produce large quantities of a sticky exudates known as honeydew, which often turns black with the growth of a sooty mold fungus. |
Treatment and SolutionsBiological ControlGreen Lacewings Ladybugs Aphid Parasites Chemical ControlInsecticidal soap, neem oil, and narrow-range oil provide temporary control if applied to thoroughly cover infested foliage. To get thorough coverage, spray these materials with a high volume of water and target the underside of leaves as well as the top. Soaps, neem oil, and narrow range oil only kill aphids present on the day they are sprayed, so applications may need to be repeated. Predators and parasites often become abundant only after aphids are numerous, so applying nonpersistent insecticides like soap or oil may provide more effective long-term control. Although these materials do kill natural enemies that are present on the plant and hit by the spray, because they leave no toxic residue, they do not kill natural enemies that migrate in after the spray. Recommended Products |
MealybugsMost adult female mealybugs are wingless, soft-bodied, grayish insects about 0.05 to 0.2 inch long. They are usually elongate and segmented, and may have wax filaments radiating from the body, especially at the tail. Most females can move slowly and are covered with whitish, mealy or cottony wax
IdentificationWoolly aphids, adelgids, whiteflies, and cottony cushion scales may sometimes be confused with mealybugs because they also produce a whitish, waxy material. The white, fluted egg sac of cottony cushion scales erupts from the female's body, which is usually bright orange, red, yellow, or brownish. Underneath the loose, cottony, waxy covering, the bodies of most aphids and adelgids appear pear shaped. Some of the aphids or adelgids in a colony may have wings, but only male mealybugs and scales have wings and males are rarely seen. Male mealybugs are tiny and delicate; the body is commonly yellow or red with two long whitish tail filaments. Life CycleMost female mealybugs lay tiny yellow eggs intermixed with white wax in a mass called an ovisac. Mealybug nymphs are oblong, whitish, yellowish, or reddish and may or may not be covered with waxy filaments. Most species feed on branches, twigs, or leaves. Depending on the species, host, and climate, they may overwinter only as eggs or as females, or as all stages. Most mealybugs have several generations a year. DamageMealybugs tend to congregate in large numbers, forming white, cottony masses on plants. High populations slow plant growth and cause premature leaf or fruit drop and twig dieback. Honeydew production and black sooty mold are the primary damage caused by most mealybugs. |
Treatment and SolutionsBiological ControlCryptolaemus montrouzieri Ladybugs Chemical ControlMealybugs are difficult to control with insecticides and systemic materials may be required. Recommended Products |
WhiteflysWhiteflies are tiny, sap-sucking insects that are frequently abundant in vegetable and ornamental plantings. They excrete sticky honeydew and cause yellowing or death of leaves. Outbreaks often occur when the natural biological control is disrupted. Management is difficult.
IdentificationWhiteflies usually occur in groups on the undersides of leaves. They derive their name from the mealy, white wax covering the adult’s wings and body. Adults are tiny insects with yellowish bodies and whitish wings. Although adults of some species have distinctive wing markings, many species are most readily distinguished in the last nymphal (immature) stage, which is wingless. Life CycleWhiteflies develop rapidly in warm weather, and populations can build up quickly in situations where natural enemies are destroyed and weather is favorable. Whiteflies normally lay their tiny, oblong eggs on the undersides of leaves. The eggs hatch, and the young whiteflies gradually increase in size through four nymphal stages called instars. The first nymphal stage (crawler) is barely visible even with a hand lens. The crawlers move around for several hours, then settle and remain immobile. Later nymphal stages are oval and flattened like small scale insects. The legs and antennae are greatly reduced, and older nymphs do not move. The winged adult emerges from the last nymphal stage (for convenience sometimes incorrectly called a pupa). All stages feed by sucking plant juices from leaves and excreting excess liquid as drops of honeydew as they feed. DamageWhiteflies suck phloem sap. Large populations can cause leaves to turn yellow, appear dry, or fall off plants. Like aphids, whiteflies excrete honeydew, so leaves may be sticky or covered with black sooty mold. Low levels of whiteflies are not usually damaging. Adults by themselves will not cause significant damage unless they are transmitting a plant pathogen. Generally, plant losses do not occur unless there is a significant population of whitefly nymphs. |
Treatment and SolutionsBiological ControlGreen Lacewings Ladybugs Pirate Bugs Chemical ControlManagement of heavy whitefly infestations is very difficult. Whiteflies are not well controlled with any available insecticides. The best strategy is to prevent problems from developing in your garden to the extent possible. In many situations, natural enemies will provide adequate control of whiteflies; outbreaks may occur if natural enemies that provide biological control of whiteflies are disrupted by insecticide applications, dusty conditions, or interference by ants. Avoid or remove plants that repeatedly host high populations of whiteflies. In gardens, whitefly populations in the early stages of population development can be held down by a vigilant program of removing infested leaves, vacuuming adults, or hosing down (syringing) with water sprays. Aluminum foil or reflective mulches can repel whiteflies from vegetable gardens and sticky traps can be used to monitor or, at high levels, reduce whitefly numbers. If you choose to use insecticides, insecticidal soaps or oils such as neem oil may reduce but not eliminate populations. Recommended Products
|
